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Rotary Gas Meters for Industrial and Commercial Applications

Rotary displacement gas meters can be employed across a wide range of applications, from residental through commercial and industrial. Their simple design provides predictable accuracy and long term durability.

Rotary Gas Meters for Industrial and Commercial Applications

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Natural gas companies worldwide use GE’s
Dresser rotary meters in commercial and
industrial natural gas measurement applications.
Our rotary meters are also used in both high
flow residential applications and low volume
transmission applications. Dresser Series C rotary
meters are used at the well head gathering line,
compressor stations, gas distribution systems,
and end users such as chemical and processing
plants. Meters of standard construction are used
in the measurement of a variety of filtered and dry
non-corrosive gases, including specialty gases.
Positive Displacement Operating Principle
Dresser rotary meters are designed to measure
the volume of gases and gas mixtures with a
high degree of accuracy. The rotary type positive
displacement operating principle assures
permanent, non-adjustable accuracy by using
two precision machined dual-lobed impellers
encased within a rigid measuring chamber.
Unlike other meter types, measurement accuracy
is not affected by changes in gas specific gravity,
pressure, or fluctuating flow. Dresser rotary
meters may be used from atmospheric pressure
to 16 bar with highly accurate measurement over
a wide operating range.
Series C Rotary Meter Design Features
■ Compact size and lower weight
■ High performance rotor (impeller) profile for
increased rangeability
■ Superior strength ensures reduced sensitivity
to pipe stress
■ Decreased susceptibility to damage from
pressure shocks
■ Simplified maintenance and repair
■ Multi-functional index
Utilizing advancements in technology and
materials, GE Oil & Gas’ innovative
Dresser Series C Rotary Meter helps reduce
installation and maintenance costs while
improving measurement accuracy
As shown in the picture, two contra-rotating impellers of
two-lobe or “ﬁgure 8” design are encased within a rigid
measuring chamber, with the inlet and outlet connections
on opposite sides. Precision machined timing gears
keep the impellers in correct relative position. Optimal
operating clearances between the impellers, cylinder and
headplates provide a continuous, non-contacting seal.

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Compact Size
The compact and space saving Dresser Series
C rotary meter is ideal for mounting in small
meter stations or cabinets.
Rotors
The precision machined, high performance
rotors are held in place with four main
shaft bearings placed outside of the timing
gears. This bearing placement strengthens
the connection between the rotors and the
timing gears. The sophisticated square profile
impellers improve not only the accuracy,
but also the rangeability of the meter by
minimizing leakage between rotors and the
body. This design also reduces the deflection
of the rotor’s main shafts at high flow rate and
elevated pressure where dynamic loading is
most prevalent. This feature makes the meter
less vulnerable to damage during start up and
operation.
Rugged Design
The Dresser Series
C rotary meter’s
rugged design
is less sensitive
to stress from
misaligned pipe or
flanged connec-
tions. Our compact
meter body, thick
flange connections, and stainless steel bearing
support rings facilitate easy installation, and
robust performance in the most demanding
installations. The square rotors with rigid main
shafts are also less susceptible to damage
from rapid pressurization of the meter.
Low Maintenance / Easy Repair
Repair technicians can replace all major parts
without special tools. This innovative Dresser
measurement cartridge simplifies most main-
tenance and repair activities. Technicians can
remove the complete measurement mechanism
(rotors, timing gears, and bearings) from the
meter body in one piece. Whether you just clean
the cartridge and re-install it, or replace the
cartridge, major repairs are fast and easy. When
regulations permit, users can also install a new
prover-certified cartridge.
Multi Functional Index
Dresser Series C rotary meters
utilize a magnetically coupled
index. A “drive” magnet couples
to the “follower” magnet of the
index, which in turn drives the
odometer on the meter index. The index can be
removed or installed with just “one twist and a
click”. The magnetic coupling allows for orienta-
tion or exchange without decommissioning the
meter.
A single index is adaptable to all Series C meter
sizes due to the gear reduction internal to the
meter body. The gear reduction is used to turn
the drive magnet at an output ratio common to
all Series C meters. By using a common index,
the design enables standardization, reduces
inventory and maximizes modular flexibility. The
Series C index also contains a pocket that can
hold different types of Low Frequency (LF) pulse
devices, such as reed switches, Wiegand sensors,
or fraud detection/tamper indication devices.

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Twin Impeller Design Reduces
Downstream Pulsation and Noise
The figure-8 lobed impeller rotary meter design
inherently creates pulsations as gas flows
through the measurement chamber. This is a
common and typical phenomenon with rotary
meters. Resonance may affect the linearity of
the calibration curve. The effect of such pulsa-
tions increases with pressure and the resultant
resonance may affect components such as
pressure regulators within the metering station.
Harmonics, or the shift in frequency created by
pulsations, can limit the achievable Qmax as the
pressure in the measuring chamber varies.
Time
ActualFlow
14%
Time
ActualFlow
<2%
Harmonics is simply a column of air being
resonated at its fundamental or lowest frequency.
The small pulsation produced by the rotary
meter occurs as the flow media quickly changes
pressure as the measuring element (impellers)
rotate. The amplitude of the pulsation from the
measurement cavity is directly proportional to the
pressure drop across the meter and the speed
of the rotating device. These resonance flow
points tend to show up as a higher than expected
nominal value on the performance curve.
The Twin impeller principle, offered in the larger
rotary meter sizes, divides the flow into two
measuring chambers. The phase of each pair of
impellers is shifted 45 degrees (180 degrees in
terms of the sine wave) so that the pulsations are
opposing and negligible, or eliminated.
Dresser Twin rotary meters provide significantly
improved accuracy over conventional rangeability
make them ideal choices for reference or master
meter applications. Reduced pulsations also
significantly reduce ambient noise, making Twin
rotary meters ideal for sound sensitive applications.
For applications requiring serial communication,
the Series C index is available with an encoder.
The encoder uses three optical sensors to detect
light passing through a specially designed
slotted disc rotating within the index. The light
detected passing through the disc is converted
to a numeric value using Gray Code. The system
offers high resolution and allows for instant
flow calculation.
The Series C index uses an 8 digit odometer and
provides direct readings in cubic meters or cubic
feet. The index is 100% sealed and is IP 65/IP 55
approved. Also, all Series C electronic devices
are ATEX 94/9/EC approved.

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Oil level sight gaugeInstallation
■ The Dresser Series C design permits very
compact M&R stations without sacrificing the
meter’s accuracy
■ All Series C meters are designed for outdoor
installation. The Index is IP 65 approved
■ Gas pipes must be clean and free from foreign
impurities such as sand, dirt, welding debris
and other particles, as well as liquid
■ Generally it is recommended that a gas filter
be installed upstream of the rotary meter,
with a 160 μ filtration size
■ Check the flow direction of the meter against
the required installation. Preferably, horizontal
flow is left to right and vertical flow is top inlet,
bottom outlet
Standard Features
The connector on the standard
mechanical index is fitted for
two LF outputs and one
tamper contact. An HF output
is available upon request.
The meters are also fitted with
a number of pressure and temperature measur-
ing connections at the inlet and outlet, suitable for
easy connection of electronic gas volume conver-
sion devices such as the Dresser Micro Corrector
and for ease in differential monitoring.
meter index
P&T Ports
The Dresser Series C meter has been designed for
rigorous natural gas measurement applications and
able to withstand typical starting up operations with-
out degradation of performance or quality. However,
to ensure an extended lifetime, care must be given
while pressurizing the meter to prevent excessive
over-speeding and damaging the rotating parts.
A single oil level indicator (sight gauge) is located
directly below the index. The oil reservoir should
be filled after the meter has been installed. A
bottle with sufficient lubrication oil for the initial
filling is supplied with every meter. The oil reservoir
should be filled until the oil level reaches the
middle of the sight glass.
Meter with external bypass option. In the unlikely event of a
ﬂow blockage, gas supply is guaranteed. An electrical contact
can be wired to activate an alarm.